The rapid activation of fire detection and suppression systems in response to a growing fire is one of the important factors required to provide for life safety and property protection. Rapid activation requires that sensors be located at optimal distances both beneath the ceiling and radially from the fire. Ceiling obstructions, such as beams and joists, and ceiling slope can significantly modify the flow of smoke along the ceiling and must be taken into consideration when a particular detection system is designed. At present, the standards used to guide the design of these systems contain very little quantitative information concerning the impact of beamed, sloped ceilings on sensor placement. A multiyear, International Fire Detection Research Project sponsored by the National Fire Protection Research Foundation (NFPRF) was initiated to provide quantitative information on the impact of beams, ceiling slope, and forced ventilation on the movement of smoke in commercial/industrial properties. During the first year of the project, numerical modeling was validated and additional simulations of level, beamed ceilings for detection of growing fires at design fire sizes of 100 kW and 1 MW were completed. It was found that conditions under beams may be equivalent in some cases to conditions in the channels between the beams at an equivalent height beneath the beam or ceiling respectively. Also, depending on detectable fire size, beam depth and beam spacing, smoke detectors or quick response fusible links may not be necessary for each beam channel. This report describes the results of the second year of the project. During the second year, numerical simulations of smoke movement in response to sloped, beamed ceilings were studied. Slopes of 10, 25 and 50 degrees were studied with beams running along or across the slope. It was found that channeling of smoke flow was more prevalent as ceiling slope increased for parallel beam cases. For beams perpendicular to the slope, increasing the ceiling slope decreased the effectiveness of the beams in preventing smoke flow up the ceiling. Based on the predicted smoke movement, recommendations on sensor selection and placement are made for sloped, beamed ceilings.
Citation: Technical Note (NIST TN) -
NIST Pub Series: Technical Note (NIST TN)
Pub Type: NIST Pubs
fire detection, field models, ceilings, fire detectors, detector response, sprinkler response, conservation, equations, heat transfer, smoke detectors, joists